One of the major challenges to HIV-1 vaccine development has been the inability of immunogens to induce broadly neutralizing antibodies (nAb). nAbs are generated during HIV-1 infection. However, most of the nAbs generated neutralize only the autologous viruses or closely related strains (Moog et al, J. Virol. 71:3734-3741 (1997), Gray et al, J. Virol. 81:6187-6196 (2007)). HIV envelope (Env) constantly mutates to escape from existing nAb response (Albert et al, Aids 4:107-112 (1990), Wei et al, Nature 422:307-312) (2003)). nAb responses do evolve over the course of the HIV infection. However, with the mutation capacity of HIV-1 viruses, neutralizing antibody responses always seem to “lag behind” virus evolution (Wei et al, Nature 422:307-312 (2003)), Richman et al, Proc. Natl. Acad. Sci. USA 100:4144-4149 (2003), Geffin et al, Virology 310:207-215 (2003)).
After extensive research, a handful of broadly neutralizing monoclonal antibodies (mAbs) against HIV-1 have been identified (Buchacher et al, AIDS Res. Hum. Retroviruses 10:359-369 (1994), Zwick et al, J. Virol. 75:10892-10895 (2001), Burton et al, Proc. Natl. Acad. Sci. USA 888:10134-10137 (1991)). Two such antibodies, 2F5 and 4E10, target the conserved membrane-proximal external region (MPER) of HIV-1, have a broad spectrum of neutralization (Binley et al, J. Virol. 78:13232-13252 (2004)), and have been shown to neutralize 80% and 100% of newly transmitted viruses (Mehandru et al, J. Virol. 78:14039-14042 (2004)), respectively. When passively administered in combination with several other broadly neutralizing monoclonal antibodies, a cocktail of mAbs composed of 2G12, 2F5 and 4E10 successfully protected the host from virus infection in animal models (Baba et al, Nat. Med. 6:200-206 (2000), Ferrantelli et al, J. Infect. Dis. 189:2167-2173 (2004), Mascola et al, Nat. Med. 6:207-210 (2000), Ruprecht et al, Vaccine 21:3370-3373 (2003)), or delayed virus rebound after cessation of antiretroviral therapy (Trkola et al, Nat. Med. 11:615-622 (2005)).
The potential of using 2F5 and 4E10 to prevent HIV infection is greatly compromised by the fact that HIV infected patients rarely develop these antibodies spontaneously (Dhillon et al, J. Virol. 81:6548-6562 (2007)), and there has been no success in inducing 2F5- and 4E10-like antibodies by vaccination (Kim et al, Vaccine 25:5102-5114 (2006), Coeffier et al, Vaccine 19:684-693 (2000), Joyce et al, J. Biol. Chem. 277:45811-45820 (2002), Ho et al, Vaccine 23:1559-1573 (2005), Zhang et al, Immunobiology 210:639-645 (2005)). Identification of subjects that develop 2F5- or 4E10-like antibodies during natural HIV-1 infection, and developing an understanding of the mechanism of, or hindrance to, these broadly neutralizing antibodies is important for AIDS vaccine design.
The present invention results, at least in part, from the identification and characterization of a rare Env mutation in the HIV-1 MPER region which is associated with an increase in neutralization sensitivity to 2F5 and 4E10 mAbs. The invention also results from the development of constructs that can modulate B cell tolerance and enhance antibody responses against poorly immunogenic HIV-1gp41MPER epitopes.